GitHub Actions: do not fail fast on Dart SDK tests.

Author: greenrobot-team

.github/workflows/dart.yml

@@ -34,6 +34,7 @@ jobs:
 
   lib:
     strategy:
+      fail-fast: false # To see all Dart SDKs that fail, also sometimes with more helpful errors.
       matrix:
         os:
           - windows-2019